<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>demo1</title>
</head>
<body>
    <div id="myDiv">
        <input type="button" value="click me" id="myBtn">
    </div>

    <script>
        const myBtn = document.getElementById('myBtn')
        myBtn.onclick = () => {
            alert('我被点击')
            // myBtn.onclick = null
            myBtn.innerHTML = 'Processing...'
        }
    </script>
</body>
</html>
